Why "too many steps"? The field is already in the registration form, it just has to be turned to "compulsory" instead of "optional". And since a setting relevant question would have to be chosen from a list one would a) have to invent a large enough pool of such questions to foil bots and b) implement a new technical function into the wiki software and c) you could not exclude that you have accumulating sleeper bots that one day strike at once.